This invention relates to a method of manufacturing a bearing in which a high-frequency hardened steel is used the composition of which does not reduce the service life of a drilling tool even if the steel is not annealed after being forged at a high temperature.
Heretofore, the flanged outer race of a bearing which is drilled, such as a hub unit ball bearing coupled to the axle of an automobile, is manufactured by using a high-frequency hardened such as SAE 1070. This steel material is a high carbon steel. Therefore, when a workpiece for manufacturing the bearing is formed with the steel material subjected to hot forging, the workpiece is high in hardness; that is, it is difficult to drill the workpiece. Hence, the hardness of the workpiece is adjusted by annealing it. That is, it is necessary to anneal the workpiece before drilling it.
However, annealing takes a relatively long period of time, thus being one of the causes which lower the productivity. Therefore, there has been a demand for provision of a bearing manufacturing method in which the annealing process is omitted.
On the other hand, as long as the conventional high-frequency hardened steel is used, even if the annealing process is omitted the bearing manufacturing method suffers from the following problem: That is, when the workpiece which is high in hardness, is drilled with a conventional drilling tool, the service life of the drilling tool is greatly reduced.